using of gm rules in design mosfet circuit ?

[hoo]

which gm rule can I use in design of simple mosfet amplifier circuit ?
after designing such circuit and thus obtaining values of Id , W/l and Vod , should three rules of gm be equal or not ?

gm rules I mean:
gm=Un*Cox*W/l*Vod
gm=2Id/Vod
gm=sqrt(2Id*Un*Cox*W/l)

 

[warlocklw]

All the gm are the same, they are derived in several forms to ease your calculation. You can pick any of them to use.

 

[hoo]

Ok thanks .

 

[pratomer]

all the gm are same, but to design a amplifier u just need to fix the Q-point and once you do so then Id and Vod are fixed hence you will not require other parameters to get gm the second equation will be enough